BR112021010941A2 - Hydraulic braking arrangement for off-road vehicles - Google Patents

Abstract

It is a provision of hydraulic braking (1) to control the front and rear brakes (2,3) of an off-road vehicle, which comprises a brake valve of hydraulic drive (5) fluidly interposed between the brakes (3) and a first source (4) of vehicle pressurized fluid and being configured to selectively allow fluid passage coming from the first source (4) to the rear brakes (3), with the hydraulically operated brake valve (5) is further configured to provide at least one hydraulic signal (8a, 8b) configured to control a relay valve (10) fluidly interposed between the front brakes (2) and a second source (12) of fluid at engine pressure. vehicle, and being configured to selectively allow the passage of fluid coming from the second source (12) to the front brakes (2) in function of at least one hydraulic signal (8a, 8b).

Description

“HYDRAULIC BRAKING ARRANGEMENT FOR OFF-ROAD VEHICLES” FIELD OF TECHNIQUE

[001] The present invention relates to a hydraulic braking arrangement for off-road vehicles, in particular an electromechanical hydraulic arrangement for agricultural vehicles.

BACKGROUND OF THE INVENTION

[002] Off-road vehicles, such as agricultural vehicles, increasingly need implementations to allow the latter to be moved efficiently across the entire possible range of vehicle working speeds.

[003] In fact, agricultural vehicles are constantly increasing their speed during road movement above 50 km/h.

Therefore, today's off-road vehicles, due to their weight and hydraulic drive, need improved hydraulic braking circuits, configured to ensure acceptable service braking of the vehicle on both the rear and front wheels.

[004] The current braking arrangement of agricultural vehicles foresees the presence of brake discs on the front axle that contribute only about 15% of the total braking force of the vehicle; in fact, most of the braking force is exerted by the rear brakes.

[005] In addition, it is increasingly requested that the front and rear brakes can be activated independently and in safety mode, that is, in a way that guarantees at least the braking of the rear wheels of one axle (rear or front) or a pair of wheels (rear left and front right, or vice versa).

[006] As mentioned above, it is necessary to allow braking of off-road vehicles in a wide range of vehicle working speeds, while containing costs.

[007] An objective of the present invention is to satisfy the above-mentioned needs in an economical and optimized way.

DESCRIPTION OF THE INVENTION

[008] The aforementioned objective is achieved by a hydraulic braking arrangement as claimed in the appended set of claims.

BRIEF DESCRIPTION OF THE FIGURES

[009] For a better understanding of the present invention, a preferred embodiment is described below, by means of a non-limiting example, with reference to the attached Figures, in which: • Figure 1 is a hydraulic schematic of a hydraulic braking arrangement of according to a first embodiment of the invention; and • Figure 2 is a hydraulic schematic of a hydraulic braking arrangement in accordance with a second embodiment of the invention.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[010] Figures 1 and 2 reveal a hydraulic braking arrangement 1 for a work vehicle comprising a pair of front 2 and rear 3 brakes, in particular a right and left front brake 2a, 2b and right and left rear brakes 3a , 3b.

[011] According to one aspect of the invention, the hydraulic braking arrangement 1 further comprises a fluid-mode hydraulically actuated brake valve 5, interposed between a pressurized fluid source 4 and the rear brakes 3. The brake valve hydraulic drive 5 is configured to receive fluid at a pre-set pressure level from source 4 and to allow such fluid to pass to the rear brakes 3 at a pressure level that is substantially the same as the pre-set pressure level above mentioned from source 4.

[012] Preferably, the source 4 is configured to supply fluid under pressure, for example, oil, at a pressure of about 100 to 120 bar, and the hydraulically actuated brake valve 5 is configured to allow the passage of such fluid. for the rear brakes 3 at the same value, which is less than the pressure drops due to the passage of fluid in the hydraulically actuated brake valve 5 itself.

[013] The hydraulically actuated brake valve 5 preferably comprises at least one first opening 7, preferably two openings 7a, 7b fluidly connected to the left and right rear brakes 3a, 3b through respective conduits 9a, 9b and at least a third opening 11 fluidly connected to the source 4, as described in more detail below.

[014] According to another aspect of the invention, the hydraulically actuated brake valve 5 is further configured to produce at least one hydraulic signal 8a, 8b configured to control a relay valve 10 fluidly, interposed between a source of fluid at pressure 12, for example from the vehicle pump or a priority valve, and front brakes 2a, 2b, as described in detail below. According to the described embodiment, the hydraulically actuated brake valve 5 generates two hydraulic signals 8a, 8b and comprises another pair of openings 6a, 6b fluidly connected to the relay valve 10.

[015] According to the exemplary disclosed embodiment, the source 4 comprises a first and a second accumulators 14', 14'' fluidly connected to the respective openings 11', 11'' in the supply brake module 5 through the conduits 15', 15''. The source 4 further comprises an accumulator charging module 16 configured to keep the accumulators 14', 14'' under certain working conditions. The accumulator charging module 16 is accordingly connected to the fluid source at pressure

12. Since the accumulator charging module 16 is known, it will not be further described in detail.

[016] According to the exemplary disclosed embodiment, the hydraulically actuated brake valve 5 comprises a first fluid-mode spool 20 interposed between the source 4, the first accumulator 14' and the openings 6a, 7a configured to allow the passage of pressurized fluid from the first accumulator 14' to the right rear brake 3a.

[017] In particular, the first spool 20 comprises a first stage 21 defining three ways and three positions, being fluidly connected to the opening 11' by means of a conduit 22, to the opening 7a by means of a conduit 23 and to a discharge 25 through a duct system 24.

[018] The first spool 20 further comprises a second stage 27, connected to the first stage 21, defining three ways and two positions, being fluidly connected to the opening 6a by means of a conduit 28, to the conduit 23 by means of a conduit 29 and an outlet 25 via a duct system 24.

[019] The hydraulically actuated brake valve 5 further comprises a second spool 20' of fluid mode interposed between the source 4, the second accumulator 14'' and the openings 6b, 7b, and configured to allow the passage of fluid under pressure from the second accumulator 14'' for the left brakes 2b, 3b.

[020] In particular, the second spool 20' comprises a first stage 21' defining three ways and three positions, being fluidly connected to the opening 11'' by means of a conduit 22', to the opening 7b by means of a conduit 23' and a discharge 25 through a system of ducts

24.

[021] The second spool 20' further comprises a second stage 27' connected to the first stage 21', which defines three ways and two positions, being fluidly connected to the opening 6b by means of a conduit 28', to a conduit 23 ' by means of a duct 29' and to an outlet 25 by means of a duct system 24 mentioned above.

[022] Preferably, the first and second spools 20, 20' are fluidly connected together to discharge 25 via a conduit system 24.

[023] Each spool 20, 20' is driven by a mechanical control input, eg given by a respective pedal 31, 31' in a known manner.

[024] The spools 20, 20' are configured to assume a first neutral position, held by the elastic members 26, 26' generating a predefined preload, in which no fluid from the accumulators 14', 14' flows to the rear brakes 3 and a possible residual fluid from hydraulic signals 8a, 8b flows to the discharge 25, and a second position, driven by the pedals 31, 31', which acts against the elastic members 26, 26', in which the fluid from the accumulators 14, 14 'flows to rear brakes 3 and hydraulic signals 8a, 8b are generated, and a flow towards relay valve 10.

[025] As stated above, hydraulic signals 8a, 8b flow to the relay valve 10 and control the latter to modulate the pressure of the fluid coming from the fluid source at pressure 12 and front brakes 2a, 2b. In particular, the relay valve 10 regulates the pressure from the source 12 at a predefined rate.

[026] In particular, the signal 8a, 8b can flow towards the openings 6a, 6b and respective openings 10a, 10b of the relay valve 10. From the openings 6a, 6b, the signals 8a, 8b converge on a relay valve. double check valve 32 which configures, for example, a direct double check valve, to select the larger of the two signals 8a, 8b. Such increased signal is fluidly connected to a valve 33 so as to control its movement against a preload force provided by an elastic member.

[027] The valve 33 is fluidly interposed between the source 12 and the front brakes 2a, 2b, and an exhaust 35, and is configured to assume a first neutral position, maintained by the elastic element 34, in which no fluid can flow. from source 12 to front brakes 2, and the second position, actuated by the largest among signals 8a, 8b, in which fluid can flow from source 12 to front brakes 2. Advantageously, valve 33 can be a three-way, three-way valve and, as stated above, hydraulically controlled.

[028] The valve 33 is configured to allow the passage of fluid from the source 12 to the brakes 2a, 2b in proportion to the pressure of signals 8a, 8b. In particular, the valve 33 can provide a higher outlet pressure compared to the pilot pressure of the hydraulically actuated brake valve 5 (signs 8a and 8b); this means that the input pressure to brakes 2a, 2b from source 12 is regulated by a ratio with pilot signals 8a, 8b.

[029] In particular, the ratio can be selected/designed over a wide range, from 1:1 to 1:10 or more, according to the maximum achievable pressure at source 12 and pilot values 8a, 8b. In general, for tractor application, the ratio is preferably between 1:1 to 1:5 or, more preferably, between 1:1 (same pressure) to 1:3 (triple pressure).

[030] In particular, the shorter the rider is in 8a or 8b and the taller the aforementioned reason may be. For example, piloting with signals 8a, 8b at 100 bar (maximum pressure of source 4) and having a pressure of source 12 of 200 bar, allows to supply brakes 2a, 2b with a pressure of 100 bar with a ratio of 1:1; similarly, piloting with signals 8a, 8b at 50 bar (for example, half the maximum pressure of source 4) and having a pressure of source 12 of 200 bar, allows to supply brakes 2a, 2b with a pressure of 100 bar with a ratio of 1:2.

[031] The operation of the above-revealed first realization is as follows.

[032] When the user presses the pedals 31, 31', the spools 20, 20' move against the preload provided by the elastic elements 26.

In this way fluid is allowed to pass from the accumulators 14, 14' to the portions 21, 21' and then through the conduits 23, 23' to the rear brakes 3a, 3b. As said, the pressure transmitted to the rear brakes 3 is regulated proportionally to the position of the spools 21 and 21' according to the travel transmitted by the driver to the pedals 31 and 31' connected to the spools.

[033] At the same time, part of the fluid from the accumulators 14, 14' flows through the portions 27, 27' and generates proportional signals 8a, 8b which flow to the relay valve 10. As mentioned herein, the The greater of the two signals triggers the movement of valve 33 against elastic preload means 34. Consequently, fluid from source 12 can flow towards front brakes 2 with a defined ratio for pilot signals 8a and 8b as mentioned above .

[034] When the accumulators 14, 14' are discharged, the refill module 16 will allow the passage of fluid under pressure from the fluid source 12 through the conduits 22 to charge the accumulators 14, 14'. In such a configuration, the spools 20, 20' are in neutral position and the pressurized fluid from the source 12 cannot pass to the brakes 2, 3 through the hydraulic actuating valve 5.

[035] Figure 2 reveals a second embodiment of the present invention, which is different from the first embodiment of Figure 1 in that it comprises a secondary brake system 40 configured, inter alia, to allow the vehicle to be parked.

[036] In particular, the secondary brake system 40 comprises an accumulator 41 fluidly connected by means of a conduit 42 to the fluid source 4, in particular, in the described embodiment, to the conduit 22 and then to the first accumulator 14'. Preferably, a non-return valve 43 is fluidly interposed in the conduit 42 so as to allow the passage of fluid only from the source 4 to the accumulator 41.

[037] The accumulator 41 is further fluidly connected to a first opening 45a of a secondary valve 45 by means of a conduit 44. The secondary valve 45 further comprises a second opening 45b fluidly connected to conduits 9a and 9b and, then to the rear brakes 3a, 3b and a third opening 45c fluidly connected to a discharge 46.

[038] Preferably, the secondary valve 45 comprises a three-way - three-position valve 47, actuated by a mechanical control input, e.g. given by a pedal/lever 48 in a known manner. Such actuation of valve 45 acts against a force given by an elastic member 49.

[039] Advantageously, the secondary brake system 40 comprises a fluid check valve 51 interposed downstream with respect to the secondary valve 45, but upstream with respect to the conduits 9a, 9b configured to allow the passage of fluid only from valve 45 for the latter.

[040] The secondary brake system 40 may further comprise a discharge valve 52 fluidly interposed between the conduit 44 and the conduit that connects the second openings 45b with the conduits 9a, 9b downstream with respect to the check valve 51, but upstream in relation to conduits 9a, 9b. Relief valve 52 is configured to allow direct passage of fluid from conduit 44 to conduits 9a, 9b without passing through secondary valve 45.

[041] Advantageously, the bypass valve 52 is a two-way, two-position ON-OFF valve and is electrically actuated thanks to an electrical signal 53, eg a remote electrical signal.

[042] The operation of the second embodiment disclosed above is as follows.

[043] The operation of the portion that is already present in the first embodiment is the same. Furthermore, the secondary brake system 40 makes it possible to brake the vehicle by means of the rear brakes 3, even in the condition of failure of the remaining portion of the arrangement 1.

[044] In fact, if necessary, the user can push lever 48 and then move valve 47 to a position where fluid contained in accumulator 41 can flow through conduit 44, through valve 47 into the conduits. 9a, 9b and then to the brakes 3a, 3b.

[045] Also, for the sake of remote control or for safety reasons, the same function may be available using bypass valve 52. In fact, signal 53 can trigger movement of valve 52 which allows direct passage of fluid from accumulator 41 through conduit 44 to conduits 9a, 9b and then to brakes 3a, 3b.

[046] When the accumulator 41 is discharged, the refill module 16 will allow the passage of fluid under pressure from the fluid source 12 through the conduit 2, the check valve 43 and the conduit 42 to recharge the accumulator 41. In this configuration, the accumulators 14', 14' are also recharged and the spools 20, 20' are in neutral position, as stated above.

[047] As seen, the advantages of a hydraulic braking system 1 according to the invention are evident.

[048] Overall braking force is increased by increasing the percentage of force applied to the front brakes relative to the rear brakes, due to increased pressure on the front brakes.

Consequently, the vehicle's braking distance is reduced.

[049] This increased force is given by the use of calipers which are driven by a dedicated high pressure source 12, regulated at a set ratio to the front brakes via a relay valve 10.

[050] It should also be noted that the pressure source 12 is independent from the pressure source 4, therefore, they can be adjusted to two different pressure levels suitable for the respective typology of front and rear brakes.

[051] Since the user-actuated pedal 31 is soft and needs low pressure to move the hydraulically-actuated brake valve 5, comfort is improved and the feel can be adapted with a wide variety of selection. In fact, the pedals don't need to create braking pressure which is fed by the accumulators, which makes them smoother and softer, compared to the brake pump pedals.

[052] In addition, there is the possibility of redundancy between the front and rear brakes 2,3, that is, there are two accumulators 14', 14'' that can allow the actuation of both brakes 2, 3. In addition, there is another redundancy in the rear brakes thanks to the secondary system 40, which allows the vehicle to be braked even if the hydraulically actuated brake valve 5 fails. Again, in the secondary system 40 itself, there is additional redundancy, thanks to valve 52, which allows system 40 to operate even if valve 47 fails.

[053] In addition, it is possible to remove the mechanical parking brake via the solenoid brake valve 47.

[054] Additionally, it is possible to achieve zero hydraulic drive functionality, as thanks to the valve 45 it is possible to reach zero speed to the parking position and then park the vehicle.

[055] It is clear that modifications can be made to the hydraulic braking system 1 described, provided that they do not extend beyond the scope of protection defined by the claims.

[056] By way of example, hydraulically actuated brake valve 5 may comprise different portions 21, 27 from those disclosed herein, and a similar consideration may apply to valve 33 and 47 or refill module 16 , which can be constructed differently.

[057] In addition, the double check valve 32 may be absent or may be a reverse double check valve; again the accumulators 14', 14' 'can be replaced by a single accumulator.

Claims (16)

1. HYDRAULIC BRAKE ARRANGEMENT (1) TO CONTROL THE FRONT AND REAR BRAKES (2,3) OF AN OFF-ROAD VEHICLE, said arrangement (1) being characterized by the fact that it comprises a hydraulically actuated brake valve (5) fluidly interposed between said rear brakes (3) and a first source (4) of fluid at the pressure of said vehicle, and configured to selectively allow the passage of fluid from said first source (4) to the said rear brakes (3), said hydraulically actuated brake valve (5) being further configured to selectively provide at least one hydraulic signal (8a, 8b) configured to control a fluidly interposed relay valve (10) between said front brakes (2) and a second source (12) of fluid at the pressure of said vehicle, and is configured to selectively allow the passage of fluid coming from said second source (12) to said front ones ( 2) depending on the d at least one hydraulic signal (8a, 8b). 2. HYDRAULIC BRAKING ARRANGEMENT, according to claim 1, characterized in that said relay valve (10) allows the passage of fluid from the second source (12) by regulating the inlet pressure of such fluid to the said front brakes (2) with a predetermined ratio that is proportional to the pressure of said pilot signals (8a, 8b). 3. HYDRAULIC BRAKING ARRANGEMENT, according to claim 2, characterized in that said ratio varies from 1: 1 to 1: 5. 4. HYDRAULIC BRAKING ARRANGEMENT, according to claim 1 to 3, characterized in that said hydraulically actuated brake valve (5) is mechanically actuated. 5. HYDRAULIC BRAKING ARRANGEMENT, according to any one of the preceding claims, characterized in that said first fluid source (4) comprises at least one accumulator (14', 14''). 6. HYDRAULIC BRAKING ARRANGEMENT, according to claim 5, characterized in that it further comprises a recharge module (16) configured to recharge said at least one accumulator (14', 14'') fluidly connecting this the latter with said second source of fluid under pressure (12). 7. HYDRAULIC BRAKING ARRANGEMENT, according to any one of the preceding claims, characterized in that said hydraulically actuated brake valve (5) comprises a first spool (20) and a second spool (20'), wherein each of said spools (20, 20') comprises a first portion (21, 21') configured to control the passage of fluid under pressure from said first source (14) to the right and left rear brakes (3a, 3b), and a second portion (27, 27') carried by said first portion (21, 21') and configured to generate said at least one hydraulic signal (8a, 8b) directed to said relay valve (10). 8. HYDRAULIC BRAKING ARRANGEMENT, according to claim 7, characterized in that said relay valve (10) comprises a hydraulically actuated valve (33) in a fluid manner interposed between said force (12) and said front brakes (2), said valve (33) being actuated by said at least one hydraulic signal (8a, 8b). 9. HYDRAULIC BRAKING ARRANGEMENT, according to claim 8, characterized in that said hydraulically actuated brake valve (5) generates two hydraulic signals (8a, 8b), respectively a first signal (8a) generated by the second portion (27) of said first spool (20) and a second signal (8b) generated by the second portion (27') of said second spool (20'), said relay valve (10) further comprising a relay valve. direct double check (32), said double check valve (32) compares said hydraulic signals (8a, 8b), the largest of which controls said valve (33). 10. HYDRAULIC BRAKING ARRANGEMENT, according to claim 8, characterized in that said hydraulically actuated brake valve (5) generates two hydraulic signals (8a, 8b), respectively a first signal (8a) generated by the second portion (27) of said first spool (20) and a second signal (8b) generated by the second portion (27') of said second spool (20'), said relay valve (10) further comprising a relay valve. reverse double check (32), said dual check valve (32) comparing said hydraulic signals (8a, 8b) and allowing control of said valve (33) only when both signals (8a, 8b) are present . 11. HYDRAULIC BRAKING ARRANGEMENT, according to any one of the preceding claims, characterized in that said second source (12) is fluidly connected to a main pump of said vehicle or to a priority valve of said vehicle. 12. HYDRAULIC BRAKING ARRANGEMENT, according to any one of the preceding claims, characterized in that it comprises a secondary brake system (40) fluidly connected to said rear brakes (3), said secondary brake system (40) is configured to control said rear brakes (3) in parallel with said hydraulically actuated brake valve (5). 13. HYDRAULIC BRAKING ARRANGEMENT, according to claim 12, characterized in that said secondary brake system (40) comprises an accumulator (41) and a control valve (47), said control valve (47) is configured to allow the passage of fluid contained in said accumulator (41) to said rear brakes (3). 14. HYDRAULIC BRAKING ARRANGEMENT, according to claim 11, characterized in that said control valve (47) is a mechanically actuated proportional valve. 15. HYDRAULIC BRAKING ARRANGEMENT, according to claim 13, characterized in that said secondary brake system (40) further comprises a bypass valve (52) in a fluid mode in parallel, in relation to the control valve ( 47), said bypass valve (52) being electrically actuated. 16. HYDRAULIC BRAKING ARRANGEMENT, according to any one of claims 13 to 15, characterized in that said accumulator (41) is recharged by said recharge module (16) by fluidly connecting said accumulator (41) with said second pressurized fluid source (12).